A Printed Circuit Board (PCB, plural PCBs) is a platform on which electronic components or devices, such as resistors, capacitors, integrated circuit packages, transistors, thyristors, transducers, switches, and many other types of electronic and electrical components, (collectively referred to hereinafter as “device” or “devices”) are rested, arranged, and electrically connected to one another as one or more circuits. A PCB with one or more devices configured thereon is called a Printed Circuit Board Assembly (PCBA, plural PCBAs).
PCBAs are common-place, and are found in almost anything that includes some electronic parts. In the simplest form, a PCB originates as a thin flat board with one side coated in a conductive material, typically copper. The devices participating in a circuit occupy one side of an example single-sided PCB.
A circuit design is overlaid on the board to identify the locations of the various devices that will participate in a circuit that will be formed using the board. The positions of the devices identify the positions of the connectors, leads, or terminals (collectively referred to hereinafter as “pin” or “pins) of the devices, e.g., the positions of connector pins of an integrated circuit, the positions of the leads of a resistor or capacitor, the terminals of a transistor, and the like. The conductive paths of the circuit connecting those pins are marked and masked on the conductive coating of the PCB.
The conductive coating is then etched, typically by using a chemical process, which removes all conductive material except the masked areas of the conductive material. The positions of the pins are drilled as holes through the board either prior to the etching or after the etching.
A pin partially or fully passes through a conductive material plated hole, e.g., a Copper plated hole, such that the pin becomes accessible from the side of the board opposite the side where the device is positioned. The pin is soldered to a conductive path that remains on the PCB after etching. This conductive path typically comprises a drilled hole that is plated with a conductive material, such as, including but not limited to Copper. This plating that is attached to the inner wall of the cylindrical hole will form a connection to inner conductive layers and conductive circuit traces that are exposed inside the hole by the drilling process. Further, this conductive structure is also connected to conductive pads that are on the top and bottom side of the hole. These pads are connected during the plating process.
The solder material is conductive material, e.g., a tin-lead alloy or silver, which is heated to a liquid state. The solder material often includes a flux material that removes any oxidation of the conductive material or other debris in the holes that might prevent the solder material from forming an acceptable electrically conducting path between the pin and the conductive path.
During the PCBA assembly process, the liquid solder material, and any flux material mixed therein, fills the conductively plated holes occupied by pins. The solder material solidifies in the holes, forming electrical connections between the pins in the holes and their respective conducting paths reaching or passing through the hole positions.
A variety of soldering techniques are used to solder the pins in the holes. Wave soldering is one example technique that causes a wave of solder material to rise on a side opposite the side where a device is positioned, and into one or more conductively plated holes occupied by a pin of the device. The solder material that rises into the holes solidifies in those holes forming electrical connections between the corresponding pins and conductive paths. The wave can rise into one or more holes occupied by a corresponding number of pins of one or more devices at a time.
Double-sides and multi-layered PCBs are used in a similar manner. For example, in a double-sides PCB, devices can be positioned on both sides of the PCB, conductive paths of the different or same circuits can be etched on both sides of the PCB, and solder can be applied from both sides for connecting the devices on the opposite sides with their respective circuits. Any number of single-sides or double-sides PCBs can be stacked to form multi-layered PCBs in a similar manner.